A conventional ultrasonic diagnostic apparatus can display in real time how the heart beats or the fetus moves, by simply bringing an ultrasonic probe into contact with body surfaces. In addition, the ultrasonic diagnostic apparatus is highly safe as compared with other medical image diagnostic apparatuses, and hence allows repeated examinations. Furthermore, the ultrasonic diagnostic apparatus is smaller in size than other medical image diagnostic apparatuses such as an X-ray diagnostic apparatus, X-ray computed tomography apparatus, magnetic resonance imaging apparatus, and nuclear medicine diagnostic apparatus, and hence can be moved to the bedside to be easily and conveniently used for examinations. In addition, the ultrasonic diagnostic apparatus is free from exposure to X-rays and the like, and hence can be used in obstetric treatment, treatment at home, and the like.
Recently, with the development of high-frequency probes and advances in image processing techniques, the resolutions of ultrasonic diagnostic apparatuses have greatly improved. With this improvement in resolution, the use of ultrasonic diagnostic apparatuses has rapidly increased in the orthopedic field in recent years. For example, in diagnosis in orthopedic examinations, an ultrasonic diagnostic apparatus sometimes displays the two ultrasonic images, side by side in one window, which are generated by scanning the left and right corresponding regions of an object (for example, the arms or legs). That is, such an apparatus often displays left and right corresponding regions of an object side by side in one window to compare an affected side with a healthy side. In some cases, the apparatus displays the two ultrasonic images obtained by imaging a similar position of an affected region at different angles.
At this time, the apparatus laterally parallelly displays the two ultrasonic images on the display screen. When observing a mammary region and a superficial musculoskeletal region, in particular, the operator often turns his/her attention to a very shallow region with a depth of about 1 cm to 3 cm from the object surface, as shown in FIG. 8. In this case, to execute laterally parallel display, it is necessary to hide left and right end portions of display images by predetermined widths so as to fit them in the display areas on the display screen, as shown in, for example, FIG. 9. In addition, as shown in FIG. 10, to execute laterally parallel display with respect to the entire field angle of a scan range, it is necessary to reduce the ultrasonic images. In any case, nothing is displayed in the lower half region of the display screen. This raises the problem of ineffective use of the display screen.
An ultrasonic diagnostic apparatus is set in advance to display two ultrasonic images on the display screen either in the laterally parallel display mode or in the vertically parallel display mode. In order to set a desired parallel display mode, the operator needs to input information to change the setting via an input device. If the apparatus allows the operator to select between the laterally parallel display mode and the vertically parallel display mode, he/she needs to select one of the display modes via the input device. In examinations in ultrasonic diagnosis in orthopedic examination, there are demands for an ultrasonic diagnostic apparatus which allows easy operation with a sense of palpation. In the orthopedic field, there are many operators who are not familiar with the operation of an ultrasonic diagnostic apparatus. For this reason, there is an increasing need to complete an examination in ultrasonic diagnosis while avoiding elaborate button operations as much as possible. There is also an increasing need to minimize the number of buttons used in an input device. It is required to make a quick diagnosis in ultrasonic examination in orthopedic examination. For this reason, the operator often makes a diagnosis without performing elaborate operations for making settings for image display. In this case, the operator sometimes does not change the standard settings for image display and makes a diagnosis upon displaying the entire musculoskeletal organ while keeping each display area large.
As described above, when executing laterally parallel display and vertically parallel display of two ultrasonic images, the operator needs to execute elaborate button operations. In addition, although the display area of each ultrasonic image which is desired by the operator can greatly change in accordance with the state of an examination, the display area is not changed and remains the same. Furthermore, the operation of setting a display area imposes some burden on the operator.